1. Field of the Invention
During the life cycle of a human hair, the hair structure is damaged to varying degrees as a result of mechanical stress, e.g. by combing or back-combing, or else as a result of chemical treatment, for example bleaching, colouring or perming. This damage impairs the surface properties of the hair, e.g. as regards gloss, suppleness or combability and generally reduces its strength. Damaged hair breaks more easily than undamaged hair.
2. Description of the Related Art
It has been known for some time that protein hydrolysates, which can be prepared by degradation of native proteins, have hair care properties. These hydrolysates chiefly contain peptides having a molecular weight in the range from 2-3 kDa and can be obtained from various protein sources, for example from cereal gluten by degreasing the gluten and then extracting it under alkaline conditions. As an example, the commonly assigned WO-A 90/05521 describes a hydrolysate which is obtained from cereal gluten, preferably wheat gluten, in a multi-stage process, and which can be used, inter alia, in hair care products. According to this specification, the dried gluten is firstly degreased using a fat solvent and then extracted using aqueous ethanol which has been rendered alkaline using NH.sub.3. The extraction residue is discarded, and the liquid phase is cooled, if necessary under full vacuum, during which a protein product is precipated out which, after being separated off, forms a clear hydrolysate composition which, at room temperature, resembles honey. This composition can be conditioned and further processed for the desired purposes.
Hydrolysates of this type are absorbed by the hair relatively uniformly and are to be found not only in the outer cell layer of scales (cuticula) of the hair, but also in the region of the fibrous shaft (cortex). Such behaviour is very desirable for the more preventive care of still largely undamaged hair. For hair which is already more severely damaged, on the other hand, a care reagent is to be aimed at which is able to recognize the damaged site, to position itself there specifically and to counter the effects of the damage. The object of the invention is to provide such a care reagent.